Hard wood floor systems are used for a variety of purposes, most notably in indoor athletic facilities, such as gymnasiums, to provide a playing surface for basketball, or racquetball for example. For athletic activities in particular, wooden floors are generally preferred over other playing surfaces because wood wears slowly and uniformly, provides high abrasion resistance and uniform resilience with only modest maintenance costs.
A typical wooden floor system is laid on a base such as a concrete or asphalt slab, or a preexisting floor. An intermediate support means or layer is secured to the base and a top layer is secured to the support surface and forms the actual playing surface. A layer of filler made of a foam or cushion material may reside between the base and the intermediate support layer or between the top layer and the intermediate layer. The top playing surface generally comprises a plurality of parallel rows of hard wood maple floorboards laid end to end and secured to the underlying support layer by nails. The thickness of the floorboards is usually a standard 25/32 of an inch, or 33/32 of an inch. The width of the floorboards is also standard, typically either 11/2" or 21/4" wide. Preferably, the floorboards in each row are staggered with respect to those in adjacent rows, for reasons which will be discussed later. Also, the relative vertical relationship between adjacent rows of floorboards is maintained by providing a tongue on one side and a mating groove on the other side of each floorboard. The floorboard tongues from one row reside within the floorboard grooves of the adjacent row.
The support means for a hard wood floor system is of critical importance. Such support layer must retain the individual floorboards in a set position. Wood floor systems undergo expansion due to ontake of moisture by the wood, either by direct application or from humidity. The relatively long, thin floorboards of a hard wood floor system are particularly susceptible to such expansion. Expansion of one floorboard will exert horizontal forces upon adjacent floorboards and result in displacement and/or warping.
Typically, to provide resiliency, the support layer is made of wood sleepers or other wood based devices. However, these substances are also susceptible to expansion from moisture and/or warping. Expansion of floorboards and/or the support means can buckle or vertically displace top portions of the floor, or even cause the securing nails to be pulled out. Moreover, if the support layer is secured to the base, expansion forces will have adverse effects on the securement means. To alleviate these problems, hard wood floor systems have recently been designed to float freely over the substrate with no mechanical attachment.
There are currently at least three types of free floating floor systems. These include a sleeper type, a single layer panel type with embedded nailing beds and a double-layer panel type.
A sleeper type system utilizes lengths of wood laid end to end in parallel rows in a direction which is perpendicular to the desired longitudinal direction of the floorboards. Typically, each sleeper is 4 feet long, 21/2" wide and 11/2" thick. The individual sleepers are staggered with respect to the sleepers in adjacent rows, and the sleeper rows are generally spaced on 12" centers.
Each individual floorboard is secured to the underlying, intersecting sleepers by driving nails diagonally through the side of the floorboard and into the sleeper below. Thus, no portion of the securing nails is exposed on the top of the playing surface.
The sleepers may not be secured to the base, thus providing a free-floating floor. While the sleepers themselves provide substantial resistance to floor buckling, there is still the possibility of sleeper warpage and resultant floor buckling. Moreover, such sleeper systems require minimum base to floor surface dimensions, due to the thickness of the sleepers. Where such a floor is to be installed over a preexisting floor, the actual floor surface may be several inches higher than the original floor, especially in older gymnasiums. This could result in extensive and expensive building modifications involving door heights, threshold treatment, basket or other equipment height adjustment and the like.
Another type of free floating floor system is commonly referred to as a panel system. In a panel system, the support layer provides an intermediate layer of wood between the playing surface and the base. The intermediate layer generally comprises a plurality of rows of panels laid end to end to cover the entire surface area of the base.
Such a panel system does not have the voids defined between the sleeper rows of a sleeper system. In a panel system, the floorboards are uniformly supported beneath the entire surface area. A panel floor system is better able to support a high point load, as compared to the sleeper system. Support for a high point load is necessary to accommodate bleachers or lift trucks, or any other heavy object which must be used to bear upon a relatively small portion of the top surface of the floor. Overall, the panel system provides equal dimensional stability in all directions.
A typical panel support system comprises a plurality of 4'.times.4' or 4'.times.8' panels, having an overall thickness of 11/8", laid end to end in parallel rows above the base. The panels typically have parallel rows of grooves milled in the top surface and aligned with the grooves of adjacent panels. Nailing beds are disposed in these grooves and are secured to the panel below, typically by some type of vertically directed fastener mechanism, or in some cases by adhesive. The floorboards are laid over the panels, perpendicular to the grooves, and secured to the beds with nails. Typically, the nailing beds comprise a metal channel filled with a wood strip, or a wood strip disposed between upper and lower metal plates. The nails are driven diagonally through the floorboards, into the strip to strike the metal base of the securing strip at the channel bottom surface and eventually curl toward the floorboard within the channel, to be clinched in place in the bed material. Some securing strips provide a thin, nail-penetratable metal layer above the wood. Floor holding nails extend through the upper metal strip into the wood nail holding strip.
Such panel systems have proved advantageous in providing dimensional stability for a free floating floor system. However, the wooden securing strips are susceptible to splitting both when the nails are inserted and through normal wear of the floor system. Moreover, use of a plurality of modular panels of this type results in a plurality of independent subfloors, with each subfloor susceptible to warping and/or tension caused by expansion of adjacent subfloors.
Although the tongue and groove relationship between adjacently lying floorboards prevents relative vertical displacement of adjacent rows of floorboards, the tongue and groove does not prevent a whole series of floorboards from being displaced vertically. Failure of the mechanical fasteners used to secure a strip to a respective panel would allow the strip, and all the floorboards attached thereto, to be displaced in an upward direction, away from the base. Once the fastening means have failed, but for the weight of the floorboards, there is nothing to restrain upward motion of the securing strip caused by expansion forces.
Another disadvantage results from the fact that, after the floorboards have been secured to the strips residing underneath, there is no way of testing or monitoring the wear and tear of the fasteners. If any of the fasteners should fail, such failure would not be discovered until after the floorboards have already warped, at a time when it is too late to correct the problem.
A further disadvantage of a panel floor system is of an economic nature. Panels of wood having dimensions of 4'.times.4' or 4'.times.8' with a thickness of 11/8" must be bought, grooved, and shipped from the manufacturer to the location where the floor is to be installed, increasing cost.
Another type of free floating floor system is commonly referred to as a double layer panel type. In a double layer panel system, the maple floorboards are secured to an upper subfloor of panels which is disposed over, and preferably secured to, a lower subfloor of panels. The floorboards are secured by securing nails which are driven therethrough and into the subfloor.
Although the double panel system overcomes some of the problems associated with the single panel system, the double panel system does not provide the advantages afforded by clinching the nails into nailing beds. Moreover, if a double panel system were adapted to utilize nailing beds, in order to clinch the nails, the tendency of the bed material to split would simply be incorporated into the floor system.
In some cases, it is desirable to insulate the floor system from a room which is located below. For example, a school might have a library located beneath a gymnasium. This can be done with acoustic matter or padding disposed below the panels. In other cases, it is desirable to make the floor more resilient. This can be done by providing a layer of close cell synthetic material beneath the panels.
In either case, the desire to insulate or make more resilient comes at the expense of the performance life of the new floor. By placing the insulating or resilient material beneath the panels, the floor is made more flexible, which is desirable. However, flexing of the floorboards tends to pull on or loosen some of the securing nails, which in turn can cause loosening or even movement of the floorboards. In some cases, the resulting differential movement of the floorboards causes the floor system to squeak or buckle during use.
It is therefore one objective of the invention to provide an improved free-floating floor, of minimal thickness and having positive floorboard securement without requiring securing strips.
A further objective of the invention has been to provide an improved free-floating, less expensive floor.
Another object of this invention is to provide a free floating panel floor system which is not susceptible to vertical displacement of adjacent floorboards or subfloor modules resulting from raising of a securing strip.
It is a still further object of this invention to provide a free floating panel floor system which individual panels are less susceptible to horizontal expansion forces caused by adjacent panels.
It is still another object of this invention to provide a free floating panel floor system which is both lower in purchase price and less expensive to ship, as compared to current systems.
It is still another object of this invention to provide a system which is long lasting, having increased resiliency without premature fastener pullout.